If you apply the Broadcast Colors effect (Effect > Color Correction > Broadcast Colors), you'll see it has two visulization options called "key unsafe" and "key safe". As the names suggest, these options will show out of range colors only or safe colors only. If you apply it to an Adjustment Layer at the top of the layer stack, it will do so for all layers in your Comp. Bear in mind that these two are visualization options, they don't legalize colors (for that you have the other options in the same effect). However, the Broadcast Color effect does not take luminance ranges into account, so you could use Color Management, or complement the Broadcast Colors effect with an instance of Levels in which Output black is set to 16 and Output white is set to 235.

The thing with Color Management is that there are values which are part of the NTSC, PAL or REC.709 (ie, HDTV) color spaces, but are still illegal because of luminance/channel values. On the other hand, if you use a color space that clips those values to legal ones when processing, it could produce bad results. So the right workflow would be: use SDTV PAL or SDTV NTSC as project working space, and then use SDTV PAL 16-235 or SDTV NTSC 16-235 as output profile, in the Color Management tab in the Output Module. This way, you'd use the full PAL or NTSC color spaces for rendering and legalize the output for the rendered file. Works beautifully. No need to use Levels or the Broadcast Colors effect to legalize color/luminance values.